Cassette condition indicating device having plug with multiple selectable positions

ABSTRACT

A tape cassette for a recording/reproducing apparatus comprises a cassette casing comprising an upper half and a lower half, a front cover provided to cover a front opening portion of the cassette casing for protecting a magnetic tape and for opening and closing the front opening portion and a locking member provided on at least one of right and left side surfaces of the cassette casing to lock the front cover when it is closed. A gap is formed between an outer side surface of the cassette casing and an inner side surface of the front cover so as to permit insertion of a member which serves to release the locking member from being locked. A projection is formed on an inner surface of the front cover covering the gap.

This application is a continuation of application Ser. No. 07/795,965,filed Nov. 21, 1991 (abandoned).

BACKGROUND OF THE INVENTION

This invention relates to a tape cassette which is most suitable for usein a recording/reproducing apparatus such as a video tape recorder orother information processing apparatus, and more particularly, to a tapecassette which has a front cover rotatably attached in the front of acassette casing to protect the surface of a magnetic tape and a rearcover pivotally supported by the front cover so as to be moved incooperation therewith and serving to cover the back of the magnetic tapewith the opening and closing operations of the front cover. In this tapecassette, vertically movable plugs are inserted in through holes formedin the cassette casing so that, when the positions of these plugs arechanged arbitrarily, an information detecting sensor provided in thevideo tape recorder is made to detect the positions of the plugs thuschanged, thereby making it possible to confirm various cassetteinformation such as the prevention of miserasing.

In this kind of tape cassette, in order to protect a magnetic tapestretched on the front side of the cassette main body, the magnetic tapeis held between the front cover and the rear cover provided rotatablyand openably in the front of the cassette main body. (See JapaneseUtility Model Unexamined publication No. 60-194787, for example.)

A conventional tape cassette of the above-described type will bedescribed below with reference to the drawings. Heretofore, this type oftape cassette has been constructed as shown in FIGS. 1 to 8.

In FIGS. 1, 2, 3 and 4, a tape cassette comprises a front cover 7, anupper half 1 and a lower half 2, in which tape cassette a pair of tapereels 3 (S side) and 4 (T side) on which a magnetic tape 5 is wound areencased. The front cover 7 has a substantially U-shaped form in crosssection, and a pair of first fulcrum pins 7b are formed integrally onthe insides of right and left lugs 7a extending from opposite ends ofthe front cover 7 and facing in parallel with each other, the fulcrumpins 7b extending inwardly while being coaxial with each other.

As shown in FIG. 2, the front cover 7 has a pair of brackets 7h formedon the inside of the top and located at positions close to the centerthereof. A pair of pin holes 7s are formed in the lower portions of thebrackets so as to be substantially coaxial with each other. A pair ofsupport pins 8a provided at right and left opposite ends of a rear cover8 are to be inserted into the pair of pin holes 7s, respectively, so asto make the rear cover 8 rotatable about the support pins 8a.

As shown in FIGS. 2 and 5, the opposite fulcrum pins 7b of the frontcover 7 formed as described above are respectively brought intoengagement with a pair of pin engaging holes 2i, if which are formed inright and left opposite side walls 2f, 1e of a cassette casing 6. A pairof second pins 8b are formed at right and left opposite ends of the rearcover 8 so as to be integral therewith and substantially coaxial witheach other and are brought into engagement with guide grooves 11 forfree sliding movement in the vertical direction. It is thereforepossible to close/open the front and rear covers substantiallysimultaneously with respect to the magnetic tape 5 stretched on thefront side of the cassette casing 6 with the rotary motion of the frontcover.

Further, as shown in FIGS. 2 and 5, the front cover 7 is rotatablyattached to the cassette casing by bringing the opposite first fulcrumpins 7b thereof into engagement with the pair of pin engaging holes 2i,1f formed in the right and left side walls 2f, 1e of the casing so thatit can rotate in directions a and a' through about 90° between twopositions where the cover is opened and closed as shown in FIG. 3,thereby serving to open and close a front opening of the cassettecasing. As shown in FIG. 4, there is provided a gap 16 between theinside of one of the end lugs 7a of the front cover 7 and the side wall2f of the cassette casing which faces on the lug concerned, and thefront cover 7 is urged to rotate in the direction of closing the coverby means of a torsion coiled spring 10 fitted on the first fulcrum pin7b. The torsion coiled spring 10 is engaged at one end 10b thereof witha spring stopper 7e projecting from the inside of one end 7a of thefront cover 7 at a position in front of the first fulcrum pin 7b and atthe other end 10a thereof with another spring stopper 1d formedintegrally with another side wall 1a of the cassette casing locatedrearwards of the first fulcrum pin 7b.

Referring to FIGS. 2 and 3, following the opening and closing operationsof the front cover 7 (bracket portions 7h), the rear cover 8 movesrotatively about the support shafts 8a while other support shafts 8b ofthe rear cover 8 are fitted and inserted into the guide grooves 11formed in the lower half 2, and therefore, it is possible to forciblyopen and close the cover at the rear of the magnetic tape. Namely, thesupport shafts 8b serve as the control shafts when the rear cover 8 isopened and closed.

Further, since the rear cover 8 is required to move smoothly when openedand closed, it becomes necessary to provide a proper play (clearance;not shown) between the guide groove 11 of the lower half 2 and theopening and closing control shaft 8b. However, too much play will resultin the deterioration of the sealing performance between the rear cover 8and the front cover 7, thereby to exert bad influence on the informationrecorded and stored on the magnetic tape due to dust and the like fromthe outside. Particularly when the cassette is turned upside down, thereis a tendency to cause a space between the front cover 7 and the rearcover 8 attributable to the individual weight of the rear cover 8itself, the size of the space being equivalent to the play.

A biasing coiled spring 12 is supported on the rotation support shaft 8aof the rear cover 8 with one end thereof pressed against the bracket 7hof the front cover 7 and the other end thereof pressed against thevicinity of the rotation control shaft 8b, and a play suitable forsmooth rotation is provided between the movement control shaft 8b andthe guide groove 11 as described above, and, at the same time, the rearcover 8 is applied with the biasing force to close the cover at alltimes. With the above construction, even if the tape cassette is usedharshly, the sealing performance between the front cover 7 and the rearcover 8 is improved so that the information recorded and stored on themagnetic tape can be protected.

In FIG. 5, in the space of a gap 47 defined by projection 2h at the rearof the first fulcrum pin 7b at one end (lug) 7a of the front cover 7, alocking member 9 is rotatably attached. The locking member 9 is formedintegrally with a pivot shaft 9a (second fulcrum) at its top end, alocking pawl 9k at its lower front and a lock releasing protrusion 9h atits rear bottom end. The pivot shaft 9a is brought into engagement withpin engaging holes 2g formed in the cassette casing so that the lockingmember 9 is made rotatable back and forth. Further, the locking member 9is urged to rotate forwardly at all times by means of a spring 13. Asshown in FIG. 6, in a state where the front cover 7 is closed, thelocking pawl 9k of the locking member 9 is brought into engagement witha protrusion 7d, which is formed integrally with the lug 7a of the frontcover 7 so as to project inwardly at a lower end position P₂ located inrear of the first fulcrum shaft 7b, from behind and below, therebylocking the front cover in the nearly closed condition.

In FIG. 5, each of the engaging holes with which the first fulcrum pins7b of the front cover 7 are brought into engagement consists of thesubstantially semicircular holes 1f and 2i formed in the verticalcombining portions of the right and left opposite side walls 1e and 2fof the upper and lower halves 1 and 2. The engaging holes 2g with whichthe pivot shaft 9a of the locking member 9 is brought into engagementare formed in the substantially U-shaped locking member receiving wallportion provided in rear of the front cover 7 and formed at the upperend of one or both of the side walls of the lower half 2 so as to have atop-opened U-shaped form. By fastening together the upper and lowerhalves 1 and 2 with screws or the like with both first fulcrum pins 7bof the front cover 7 kept in engagement with the holes consisting of theupper and lower semicircular holes and with the right and left oppositeends of the pivot shaft (second fulcrum) 9a of the locking member 9 keptin engagement with the pin engaging holes, the front cover 7 and thelocking member 9 can be rotatably attached separately without anypossibility of their coming off.

As the tape cassette having the above construction is loaded into theVTR (not shown), a lock releasing member 14 which can project from theVTR side is made to come in contact with the lock releasing protrusion9h (9j) of the locking member 9 as shown in FIG. 6, so that the lockingmember 9 is moved back rotatively about the pivot shaft 9a and thelocking pawl 9k is disengaged from the protrusion 7d of the front coverto release the locked condition. Then, a cover opening member (notshown) formed on the VTR side is inserted into a space 16 definedbetween the front cover 7 and the cassette casing side wall steppedsurfaces 1e, 2f so as to push up an end face 7p of the front cover 7against the biasing torsion coiled spring 10 and, at substantially thesame time, the bracket 7h formed integrally with the front cover 7 isrotated about the first fulcrum pin 7b and, further, the pushing forceis transmitted to the support pin 8a of the rear cover 8 which issupported by the bracket 7h at all times. In this case, contrary to thecover closing operation, the rotation control pin 8b of the rear cover 8is moved toward the upper part of the cassette within the guide groove11 of the lower half 2 against the biasing force of the torsion coiledspring 12, so that the rear cover 8 which has been served to protect theback of the magnetic tape is separated therefrom and the front cover 7is separated from the surface of the magnetic tape. In this way, thecovers are removed to open an opening L, thereby completing the loadingof the magnetic tape in the VTR.

Next, description will be given of the construction for the judgement ofvarious types of cassette information such as the prevention ofmiserasing in this kind of conventional tape cassette, that is, theconstruction in which the cassette is formed with through holes atplural points thereof and in which vertically movable plugs are disposedin these through holes so that positions of the plugs can be changed asdesired, by referring to the drawings.

Referring to FIGS. 9 and 13, the cassette casing 6 consists of the upperand lower halves 1 and 2, and the reels 3 and 4 on which the magnetictape 5 is wound are rotatably encased in the cassette casing 6. Thefront cover 7 is rotatably attached to the front end portion of thecassette casing 6, and the rear cover 8 capable of being opened andclosed following the rotation of the front cover is further attachedthereto. In addition, the cassette casing 6 is formed with threevertical through holes 20' (21', 20") at points located on right andleft of the front part thereof and at a point located at the center ofthe rear part thereof. The through holes 20', 21', 20" formed on theback side of the cassette at the points located on right and left of thefront part thereof serve as reference holes for positioning when thecassette casing is to be loaded in the recording/reproducing apparatussuch as the video tape recorder. Within these through holes 20' (21'),plugs 28' are inserted respectively, and within through hole 20", plug28" is inserted.

Referring next to FIGS. 10a and 10b, each plug 28' is formed at itsupper end with a tool insert groove 28b' and at its lower end with aprotrusion 28d' which projects in the horizontal direction, and twoupper and lower stepped portions 24' and 25' are formed in the throughhole at different angular positions. The plug is to be inserted in thethrough hole while being urged by a spring so as to bring the horizontalprotrusion at the lower end of the plug into engagement with either ofthe two upper and lower stepped portions 24' and 25'. By so doing, thevertical position of the plug in the through hole can be changed.

Referring to FIGS. 13, 10A and 10B, cylindrical projecting portions 18',18" and 19', 19" are formed in the upper and lower halves 1' and 2',respectively, so as to meet at surface 29' and form the through holes20',20", the surfaces 24' and 25' for restricting the vertical movementof the plug 28' (slit-like upper and lower positioning portions, theveritcal and angular positions of which differ from each other in thethrough hole), and, further, the positioning and sensor insertion holes21' when the cassette is to be loaded in the VTR.

The plug 28' is formed in the top end part thereof with a crown portion28a' and the tool insert groove 28b' which can be handled from theoutside by means of a screw-driver 42' or the like, and a coiled spring40' serving to apply an elastic biasing force is disposed around thecylinder part located between the crown portion 28a' and the lower endprotrusion 28d'.

The through hole 20' serves both as the insertion hole through which thecrown portion 28a' of the plug is to be moved elastically and as therotative operation range of the tip end of the screw-driver.

Referring to FIGS. 10A to 12B, when it is intended to move within thecassette casing 6 the plug 28' which has the elastic coiled spring 40'disposed between the crown portion 28a' and the lower end protrusion28d', the tip end of the screw-driver 42' is brought into engagementwith the groove 28b' formed in the crown portion 28a' of the plug 28'from the outside so as to press down the plug 28' until the lower endprotrusion 28d' of the plug 28' is engaged with and inserted into theinsertion groove formed in the upper half 1 and goes downwards in thevertical direction beyond the lower surface of the cassette casing 6against the elastic coiled spring 40' as shown in FIG. 11. In thisstate, the plug 28' is rotated about the axis thereof in the directionof R' through 180° so as to fix the position of the lower end protrusion28d' at the point where either of the slit-like positioning portions 24'and 25' is formed in the cassette casing 6 due to the elastic restoringforce of the coiled spring 40'. In this way, the vertical position ofthe plug 28' can be changed within the through hole 21'.

On the other hand, a position detective sensor pin 41' is formed uprighton the VTR apparatus for free vertical movement for transferring asignal to the VTR apparatus according to the vertical position at whichthe position detective sensor 41' comes in contact with the lower endportrusion 28d' of the plug 28' and, further, with a lower end surface28e', so as to prevent the re-recording of information or the miserasingof the information recorded already on the magnetic tape.

FIG. 11 shows the operation for moving the plug 28' from the upperposition 25' to the lower position 24'. Namely, in the state where thetip end of the screw-driver 42' is brought into engagement with thegroove 28b' formed in the crown portion 28a' so as to press down theplug 28' until the lower end protrusion 28d' of the plug 28' is engagedwith and inserted into the insertion groove formed in the upper half 1and goes downwards vertically beyond the lower surface of the cassettecasing 6 against the elastic coiled spring 40', the plug 28' is rotatedin the direction of R' through 180°.

Then, as the plug 28' is moved to the position where the plug lower endportrusion 28d' engages with another vertical groove, the elasticrestoring force generated by the coiled spring 40' is transmitted to theplug 28' so that the lower end protrusion 28d' is received in the lowerpositioning portion 24' as shown in FIGS. 12A and 12B. On the otherhand, the operation for moving the lower end protrusion 28d' from thelower positioning portion 24' to the upper positioning portion 25' isreverse to the operation described in connection with FIG. 11, that is,in the state where the lower end protrusion 28d' is pressed down untilit goes beyond the lower surface of the cassettte casing 6 due to theoperation performed from above, the plug 28' is rotated in the directionopposite to the direction of R' through 180° so as to make the lower endprotrusion 28d' engage with the other vertical groove likewise. As aresult, the lower end protrusion is received in the upper positioningportion 25' due to the elastic restoring force generated by the coiledspring 40.

However, the conventional tape cassette of this kind has the followingproblem. Namely, as shown in FIGS. 4 and 6, in the conventional tapecassette, it becomes necessary to provide the space 16 and the frontcover face 7p for enabling, when the tape cassette is loaded in the VTR,the cover opening member (not shown) formed on the VTR side to open thefront cover of the tape cassette after releasing the locked condition bythe contact of the locking releasing member 14 with the releasingprotrusion 9h (9j) of the locking member as shown in FIG. 6, and hence,it is necessary to provide a gap S between the cassette casing 6 and thefront cover 7.

In FIG. 14, the tape cassette (casing 6) which comprises theabove-described front cover 7 and the rear cover 8 is provided with thelugs 7a, first stepped surfaces 1e, 2f which are formed in one or bothof the side walls of the cassette casing 6 and which have the thicknessequal to that of the lug 7a on which the pivot shaft is formed, andtapered second stepped surfaces 1g, 2j which are formed forwardly of thefirst stepped surfaces 1e, 2f in the cassette casing, so that there canbe assured and provided between the front cover lug 7a and the secondstepped surfaces 1g, 2f the space 16 through which the front coveropening member formed on the VTR side is made to pass as well as the gapS. On the other hand, the front cover 7 is formed at the lower endthereof with the stepped surface 7p with which the cover opening memberis made to come in contact.

As the cassette casing 6 is loaded in the VTR apparatus, the lockreleasing member 14 of the VTR is made to come in contact with the lockreleasing projection 9h (9j) of the locking member 9 of the tapecassette as shown in FIG. 6, so as to release the lock for preventingthe front cover 7 from being opened. Then, as soon as the cassettecasing 6 is positioned in the standard position in the VTR in a shorttime, the front cover opening member (not shown) formed on the VTR sideis inserted through the gap S so as to perform the cover openingoperation against the biasing torsion provided by biasing torsion coiledspring 10.

In FIG. 14, the front cover opening member formed on the VTR is requiredto have a proper width from the viewpoint of the strength. Further, inconsideration of the scatter in the positional accuracy of attaching,the proper width S of the space 16 becomes necessary. Increase of thewidth S contributes to the improvement of the chucking reliability ofthe VTR at the time of opening the cover, but too large a width Sinterferes with the loading area for tape travelling in the cassette.Accordingly, it is necessary that the width S take a proper value whichcan satisfy these two conditions.

If an impact load is applied to the corner of the front cover 7 of theabove-described tape cassette in the direction of W (when the tapecassette is dropped, for example) as shown in FIG. 14, not only is thelug 7a on which the pivot shaft of the front cover is formed deformed(moved) elastically within the gap S, but also, the corner of the frontcover lug 7a is cracked, or the lug 7a is broken at the corner, so thatit becomes impossible to open and close the front cover, resulting inthe fatal defect of the cassette that the recorded information is lostdue to exposure of the surface of the magnetic tape 5 to dust from theoutside, fingerprint, moisture, smoke or the like.

Further, if a load is applied to the corner of the front cover 7 in thedirection of W so that the lug 7a on which the pivot shaft is formed isdeformed elastically within the gap S, if the strength of the corner ishigh enough to prevent the cracking, the reaction force causes the pivotshaft 7b of the front cover to come off from the cassette casing 6 or tobe broken to make it impossible to open and close the front cover itselfwhile the magnetic tape surface is being exposed, resulting in the fataldefect noted above.

Further, if a load is applied to the corner of the front cover in thedirection of W so that the lug 7a on which the pivot shaft of the frontcover is formed is deformed elastically within the gap S and the frontcover corner, the pivot shaft 7b and the engaging holes 1f, 2i of thecassette casing have the impact strength, since the rear cover 8 itselfand the movement thereof are held and controlled by a pair of guideshafts 8b between a pair of guide grooves 11 provided in the cassettecasing 6 as shown in FIGS. 9 and 14, the impact force is transmitted tothe brackets 7h formed on the inside of the front cover 7 for pivotallysupporting the rotary shafts 8a of the rear cover, with the result inthat the brackets 7h are broken so as to cause the rear cover 8 to bedisengaged from the tape cassette. If the rear cover 8 is disengagedfrom the tape cassette, since the tape 5 is damaged and the back of themagnetic tape is exposed, the information recorded and stored is lost asmentioned before, resulting in the fatal defact as well.

The above-described conventional tape cassette further has the followingproblem. Namely, as shown in FIGS. 15 and 16, from the viewpoint of thedesign of the conventional tape cassette, in order to detect theterminal end of the tape reel, holes 7c and 2c through which thephotodetective optical path is made to pass and which are formed in thefront cover 7 and the cassette casing 6, must be aligned with each otherwhen the front cover is fully opened. The locking protrusion 7d' formedbeforehand integrally on the inside of one or both of the lugs 7a at theopposite side ends of the front cover 7 can be released from the coverclosing condition after the front cover 7 is permitted to rotate upwardsof the cassette casing at the time when the locking member 9 istemporarily rotated backwards of the cassette casing by an externalmeans such as the releasing member 14 of the VTR, for example, as shownin FIG. 6, that is, at the time of releasing the locked condition. Inthis case, since the locking member 9 is always urged rotatively towardthe front of the cassette (or in the direction of locking the cover)about the pivot shaft 9a by means of the spring 10 (13) or the like, ifthere is exerted no external constraining force to the biasing force Pb,the locking member 9 is allowed to move easily within the movable rangeas shown in FIG. 15. In consideration of the cumulative moving backlashof the cassette in the VTR and, further, the cumulative attachingbacklash of the lock releasing member 14 and the like, it is easilypossible to cause the lock releasing member 14 to strike at the air. Asshown in FIG. 15, since the optical path 2c along which a ray of lightis made to pass when the cover is opened is covered with the lockingpawl 9k of the locking member and the vicinity thereof, it is impossibleto detect the terminal end of the tape so as to bring about themalfunction. Further, as shown in FIG. 16, in case that the front covertends to rotate in the cover closing direction due to the biasing forcePf' with the locking member being rotated forwardly of the cassette dueto the biasing force Pb' of the spring 10 or the like, the lockingprotrusion 7d' formed on the inside of the front cover 7a comes intocontact with a surface 9e of the locking member so that the front coverand the locking member are restrained unreasonably so as to be broughtto a standstill relative to each other. If they are kept in this state,not only can the tape cassette not be ejected out of the VTR, but also,the VTR or the cassette casing may by damaged if ejection by force istried. In addition, if the locking member 9 is returned to its regularposition unexpectedly, the front cover is rotated in the cover closingdirection irrespective of the position of the magnetic tape drawn out,with the result in that the magnetic tape is damaged to cause theinformation recorded and stored thereon to be lost. This is a seriousdefect that can take place whether the cassette casing exists inside oroutside of the VTR.

In the state shown in FIG. 16, if it is tried to push the front cover byforce in the cover closing direction, the abutting force between thefront cover and the locking member is increased to damage either member,thereby making it impossible to fulfill the prescribed function.

Moreover, the conventional tape cassette of this kind has the followingproblem. Namely, as shown in FIG. 17, it is necessary in the first placeto insert (or temporarily fit) the plug 28' in the cassette upperhalf 1. In this case, since the vertical insertion groove with which anupper surface 28c' of the plug lower end protrusion 28d' is brought intoengagement is not formed in the through hole 20' of the cylindricalprojecting portion 18', the plug 28' itself is inclined in the directionX within the range of the plug receiving portion 20' and, further,pressed down against the biasing force Z' produced by the coiled spring40' until the lower end protrusion 28d' goes beyond the plug lowerpositioning portion 24' of the upper half 1, that is, the position ofgreater displacement. For this reason, the operation is very complicatedand requires sufficient experience in practice.

Then, the upper and lower halves are to be coupled together and fastenedwith screw or the like. By so doing, after the plug 28' is movedvertically and rotated about the axis thereof through about 180°, thevertical position of the plug 28' can be changed. However, since thepositioning portions 24' and 25' with and by which the plug lower endprotrusion 28' is brought into contact and positioned are provided inthe upper and lower halves, respectively, with their heights and angularpositions being different from each other, the structure of moldsbecomes complicated and, at the same time, it is difficult to mold thesehalves, with the result in that the cost is increased and, further, itbecomes liable to cause the scattering because the upper and lowerpositions are constructed by the combination of the upper and lowerhalves.

In addition, in case of changing the plug itself between the upper andlower positions, since the stroke is so long that the plug lower endprotrusion 28d' must be moved down to the lower surface of the cassettecasing 6', the elastic reaction force of the spring becomes largenaturally with the increase of the stroke, resulting in the operationaldifficulty as well.

Moreover, since the upper and lower halves are simply joined face toface with each other, if an unexpected high load is applied to thecassette casing 6 due to drop impact or the like, an offset U is causeddue to disagreement between the cylindrical projecting portions of theupper and lower halves as shown in FIG. 18, so that the plug 28' assumesan aspect reverse to that assumed when it is temporarily fixed in theupper half. As a result, a spring biasing reaction force is exerted onthe plug 28' so that the plug 28' is disengaged upwards from thecassette casing, thereby giving rise to a fatal defect that theprescribed function cannot be fulfilled.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems of the prior arts, the presentinvention is achieved. Therefore, an object of the invention is toprovide a tape cassette which can solve the above-mentioned problems.

According to an aspect of the present invention, there is provided atape cassette for a recording/reproducing apparatus comprising acassette casing comprising an upper half and a lower half, a front coverprovided to cover a front opening portion of the cassette casing forprotecting a magnetic tape and for opening and closing the front openingportion and a locking member provided on at least one of right and leftside surfaces of the cassette casing to lock the front cover when it isclosed, wherein a gap is formed between an outer side surface of thecassette casing and an inner side surface of the front cover so as topermit insertion of a member which serves to release the locking memberfrom being locked, and a projection is formed on an inner surface of thefront cover covering the gap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembly perspective view of a first conventional tapecassette, showing essential portions of component parts thereof;

FIG. 2 is a disassembled perspective view of the same tape cassette,showing essential portions of the construction thereof;

FIG. 3 is a side view of the same tape cassette, showing a front coverin its closed and opened positions;

FIG. 4 is a plan view showing the construction of the same conventionaltape cassette;

FIG. 5 is a disassembled perspective view of the conventional tapecassette, showing essential portions of the construction thereof;

FIG. 6 is a sectional assembly view of the conventional tape cassette,showing essential portions of component parts thereof when a lockingmember is in the engaged state;

FIG. 7 is a detailed (sectional) view showing the assembly and fittingof the component parts of the same conventional tape cassette when adetection plug is held in its upper position;

FIG. 8 is a detailed (sectional) view showing the assembly and fittingof the component parts of the same conventional tape cassette when thedetection plug is being operated;

FIG. 9 is an assembly perspective view of a second conventional tapecassette;

FIG. 10A is a detailed view showing the assembly and fitting of thecomponent parts of the same conventional tape cassette when thedetection plug is held in its lower position;

FIG. 10B is an assembly cross-sectional view along line XB--XB of FIG.10A of the component parts of the same conventional tape cassette whenthe detection plug is held in its lower position;

FIG. 11 is a detailed (sectional) view showing the assembly and fittingof the component parts of the same conventional tape cassette when thedetection plug is being operated;

FIG. 12A is a detailed (sectional) view showing the assembly and fittingof the component parts of the same conventional tape cassette when thedetection plug is held in its lower position;

FIG. 12B is a cross-sectional view along line XIIB--XIIB of FIG. 12Ashowing the assembly and fitting of the component parts of the sameconventional tape cassette when the detection plug is held in its lowerposition;

FIG. 13 is an assembly perspective view of the same conventional tapecassette;

FIG. 14 is an assembly sectional view showing essential portions of thecomponent parts (of the conventional tape cassette) concerned with thefirst subject;

FIG. 15 is an assembly sectional view along line XV--XV of FIG. 14,showing essential portions of the component parts (of the conventionaltape cassette) concerned with the second subject (when the lockingmember gets in deeply);

FIG. 16 is an assembly sectional view along line XV--XV of FIG. 14,showing essential portions of the component parts (of the conventionaltape cassette) concerned with the same object (when the locking memberis brought in the unexpected state);

FIG. 17 is a disassembled (sectional) view showing the assembly andfitting of the component parts (of the conventional tape cassette)concerned with a third subject when the detection plug is beinginserted;

FIG. 18 is a detailed (sectional) view shwoing the assembly and fittingof the component parts concerned with the same subject when the cassettecasing is brought into an unexpected state;

FIG. 19 is an assembly sectional view showing essential portions ofcomponent parts of a tape cassette according to a first embodiment ofthe present invention;

FIG. 20A is an assembly sectional view showing essential portions of thecomponent parts of the first embodiment of the invention;

FIG. 20B is a vertical sectional view, along line XXB--XXB of FIG. 20A,showing essential portions of the component parts of the same embodimentof the invention;

FIG. 21 is an assembly sectional view showing essential portions of thecomponent parts of the first embodiment of the invention;

FIG. 22A is a perspective view showing essential portions of thecomponent parts of the same embodiment;

FIG. 22B is a perspective view showing essential portions of thecomponent parts of the same embodiment;

FIG. 22C is a view of the component parts of the same embodiment, asseen from the direction of an arrow XXIIC;

FIG. 23 is an assembly sectional view showing essential portions of thecomponent parts of a tape cassette according to a second embodiment ofthe invention (when a front cover is closed);

FIG. 24 is an assembly sectional view showing essential portions of thecomponent parts of the second embodiment of the invention (when thefront cover is opened);

FIG. 25 is an assembly sectional view showing essential portions of thecomponent parts of the same embodiment of the invention (when a lockingmember is held in the engaged state);

FIG. 26A is a perspective view showing essential portions of thecomponent part (front cover) of the same embodiment of the invention;

FIG. 26B is a perspective view showing essential portions of thecomponent part (lid lock lever) of the same embodiment of the invention;

FIG. 27A is a (sectional) view showing the assembly and fitting of thecomponent parts of a tape cassette according to a third embodiment ofthe present invention when a detection plug is held in its lowerposition;

FIG. 27B is an assembly cross-sectional view along line XXVIIB--XXVIIBof FIG. 27A of the component parts of the third embodiment of theinvention when the detection plug is held in its lower position;

FIG. 28 contains two views one of which is a disassembled perspectiveview of the first embodiment of the invention showing essential portionsof the component parts thereof (on the second standard side) and theother of which is a disassembled perspective view of the firstembodiment of the invention showing essential portions of the componentparts thereof (on the first standard side);

FIG. 29A is a disassembled (sectional) view showing the assembly andfitting of the component parts of the same embodiment when the detectionplug is being inserted;

FIG. 29B is an assembly cross-sectional view along line XXIXB--XXIXB ofFIG. 29A, of the component parts of the same embodiment when thedetection plug is being inserted;

FIG. 30A is an assembly (sectional) view of the component parts (upperand lower halves) of the same embodiment when the plug is being set;

FIG. 30B is a view showing the assembly and fitting of the componentparts (upper and lower halves) of the same embodiment;

FIG. 31A is a detailed (sectional) view showing the assembly and fittingof the component parts of the same embodiment when the detection plug isheld in its upper position;

FIG. 31B is a cross-sectional view, along line XXXIB--XXXIB of FIG. 31A,showing the assembly and fitting of the component parts of the sameembodiment when the detection plug is held in its upper position;

FIG. 32 is a detailed (sectional) view showing the assembly and fittingof the component parts of the same embodiment when the detection plug isheld in its lower position;

FIG. 33 contains two views one of which is a disassembled perspectiveview of the first embodiment of the invention showing essential portionsof the component parts thereof (on the second standard side) and theother of which is a disassembled perspective view of the firstembodiment of the invention showing essential portions of the componentparts thereof (on the first standard side);

FIG. 34A is a perspective view of the component part (detection plug) ofthe same embodiment;

FIG. 34B is a perspective view of the component part (detection plug) ofthe same embodiment;

FIG. 34C is a perspective view of the component part (detection plug) ofthe same embodiment;

FIG. 35A is a development showing the fitting of the component parts(plug, upper and lower halves) of the same embodiment (when a verticalrib is formed);

FIG. 35B is a development showing the fitting of the component parts(plug, upper and lower halved) of the same embodiment (when the verticalrib is not formed);

FIG. 36A is a development showing the fitting of the component parts ofanother embodiment (when a vertical rib is formed);

FIG. 36B is a development showing the fitting of the component parts ofanother embodiment (when the vertical rib is not formed);

FIG. 37A is a development showing the fitting of the component parts ofstill another embodiment (when a vertical rib is formed);

FIG. 37B is a development showing the fitting of the component parts ofstill another embodiment (when the vertical rib is not formed);

FIG. 38 is an assembly sectional view of the component parts of a fourthembodiment of the present invention showing the position in which a reelmount is set; and

FIG. 39 is a plan view of the component parts (upper half, clear window)of the same embodiment (showing vertical circumferential ribs).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Description will be given below of a tape cassette for video taperecorder according to an embodiment of the present invention withreference to the drawings. The general structure of the tape cassette ofthis embodiment is partially identical with that of the conventionaltape cassette shown in FIGS. 1, 2 and 5. In this embodiment, essentialportions will be described with the same component parts as those of theconventional tape cassette being designated by the same referencenumerals and explanation thereof being omitted.

In the tape cassette of this invention, as shown in FIGS. 19, 20, 21 and22, a pair of pivot shafts 7b (having heads 7r) of a front cover 7 arebrought into engagement with engaging holes 1f, 2i formed in thecassette casing 6 and a coiled spring 10 is used to close the frontcover 7. A pair of brackets 7h provided on the inside of the front cover7 are each formed with pivot holes 7s into which a pair of support pins8a of a rear cover 8 are inserted respectively so as to make the rearcover 8 rotatable about the support pins 8a. A pair of second supportpins 8b are provided in the lower portions of opposite ends of the rearcover 8 so as to be brought into engagement with guide grooves 11 of thecassette casing 6, thereby permitting the rear cover 8 to be closed frombehind the back of the magnetic tape. In this way, both sides of themagnetic tape 5 can be protected as the tape travels through a pathdefined at least in part by posts 50 and portion 4s of reel 4. One orboth of the lugs 7a of the front cover 7 are formed with a plurality ofprojections 15A or 15B, accommodated by indentation 2e, on the insidesurface thereof on which the pivot shaft is formed, so as to secure asphere S into which a cover opening member provided on the VTR is to beinserted as well as to restrict the moving distance of the front cover 7in the longitudinal direction thereof within the range of a gap Tdefined between the plural projections 15A or 15B and the cassettecasing 6.

On the other hand, as shown in FIGS. 21 and 22A-22C, an L-shaped rib 15Cis formed integrally with the front cover 7 so as to extend from theinside of the lug 7a to a magnetic tape protective surface 7u, and thegap T is provided between the L-shaped rib and the cassette casing 6 asmentioned before. The L-shaped rib 15C is installed among three surfacesincluding the pivot shaft forming surface 7a, the tape protectivesurface 7u and a front cover top surface 7v so as to increase thestiffness to an impact load to be applied in the direction of W (shownin FIG. 14), restrict the displacement within the range of T, absorb andlessen the impact due to the rib effect, and prevent the front cover 7and the rear cover 8 from being damaged and cracked while protecting themagnetic tape 5 perfectly, thereby giving rise to no fatal defect suchas loss of the information recorded and stored on the magnetic tape 5.Also, one of lugs 7a has protrusion 7d integrally formed with projection7 i which has rear surface 7w.

Further, it is also effective to increase the stiffness of the bracket7h by providing a reinforcing rib 7t in the bracket 7h of the frontcover 7 as shown in FIG. 8 in connection with the prior art, andhowever, it is much more effective from the viewpoint of the cassettestructure to increase the stiffness by making use of the abovetechnique.

The present invention has been described above in connection with anembodiment, and however, the invention is not limited to this embodimentbut can be modified variously and effectively based on the technicalidea of this invention.

For example, the plural projections 15A or 15B on the inside of the lug7a of the front cover 7 may be formed as a single body extending in thethicknesswise direction of the cassette or may be formed as a singlebody extending in the widthwise direction of the cassette, and,furthermore, the rib is not limited to the L-shaped one but may be aC-shaped one.

The present invention is applicable not only to the tape cassette foruse in the video tape recorder but also to tape cassettes for use invarious recording/reproducing apparatus which record and reproducevarious informations by means of various recording and reproducingmethods.

As described above, according to the present invention, the sphere Sinto which the front cover opening member of the VTR is to be insertedand the space 16 are ensured in the tape cassette so that, even if animpact load is applied to the tape cassette, particularly to the frontcover 7 unexpectedly, the displacement of the front cover can berestricted within the range of the gap T provided between the pluralprojections 15A, 15B, 15C and the cassette casing 6 and the impact forcecan be absorbed and lessened by the plural projections 15A, 15B, 15C soas to prevent the front cover 7 and the rear cover 8 from being damagedand cracked. In consequence, it is possible to protect perfectly themagnetic tape 5 and the information recorded and stored thereon, therebygiving rise to no fatal defect.

Further, to form the plural projections 15A, 15B integrally on theinside of the lug 7a of the front cover 7 can be realized easily bymaking use of a die of simple structure, resulting in an extremelyreduced cost and an unquestionable effect.

Next, a second embodiment of the present invention will be describedwith reference to the accompanying drawings. The general structure ofthe tape cassette of this embodiment is partially identical with that ofthe conventional tape cassette shown in FIGS. 3 to 6, 15 and 16. In thisembodiment, essential portions will be described with the same componentparts as those of the conventional tape cassette being designated by thesame reference numerals and explanation thereof being omitted.

In the tape cassette of the present invention, as shown in FIGS. 26A and26B, a lug 7a of a U-shaped front cover 7, having an outer surface 7k,is formed integrally with a locking protrusion 7d on the inside thereof,and a flat or stepped straight or tapered surface 7i is further formedcontiguously or discontiguously to the locking protrusion 7d to stand ina row, so that the movement of a locking member 9 is controlled due tocontact with them from the time just before the cover is closed to thetime when the cover is to be opened next. In addition, as a measure forcontrolling the movement of the locking member, contact surfaces 7l and7g of the projecting portion of the front cover consists of flat surfaceportion and curved surface portion and another contact surfaces 9g and9f of the locking member also consists of flat surface portion andcurved surface portion. Upper half 1 has inner surface 1b, and tape 5 isat least partially in contact with portion 17. Spring stopper 7e hasprojection 7m thereon. Projection 7d has rear surface 7n. Locking member9 has gap 9c formed therein with inner surface 9b.

According to the tape cassette of this invention, even when the frontcover is fully opened as shown in FIG. 24, it is hardly caused due to anoverlapping area α between the contact engaging surfaces that thelocking member 9 gets in too deeply between the front cover and thecassette casing to cover the optical path passing through the hole fordetecting the terminal end of the tape wound on the reel as shown inFIGS. 15 and 16 or make the tape cassette inoperative, thereby improvingthe reliability as for the cassette. Further, the locking member 9 isnormally applied with a biasing force Pb by means of a biasing spring 10toward the front of the cassette casing about the second support pivot,and therefore, the front cover can be locked and unlocked automaticallydepending upon the state of contact between the engaging surfacesbrought about as a result of rotation of the front cover. In this way,the cover can be locked reliably and firmly when it is closed.

In FIG. 24, the locking member 9 is made to move toward the front of thecassette casing by the action of the biasing force Pb, but, the movingdistance thereof is controlled by the contact of one end surface 9e ofthe locking member releasing projection with the surfaces 7g and 7lformed at opposite ends of the cassette. When it is intended to make thefront cover 7 rotate in the cover opening direction in the state shownin FIG. 25, since an engaging area β between the locking protrusion 7dof the front cover and the locking pawl 9k of the locking member isincreased and since the lock releasing projection 9h is restrained frommoving by a surface 2b of recess 2d of the lower half 2, which contactssurface 9i of projection 9h, the locking force becomes greater than theturning force, thereby perfectly preventing the locking member frombeing released.

The present invention has been described above in conjunction with anembodiment, and however, the invention is not limited to this embodimentbut can be modified variously and effectively based on the technicalidea of this invention.

For example, the contact surfaces 7g and 7l formed on the inside of thefront cover 7a so as to be brought into contact with the locking membermay be formed entirely by a curved surface or a straight surface aswell. Further, the engaging surfaces 9d and 7f between the lockingprojection of the locking member and the locking protrusion of the frontcover may be formed at proper angles.

Incidentally, the present invention is applicable to tape cassettes foruse in various recording/reproducing apparatus other than the video taperecorder and in other information processing apparatus.

As described before, according to the present invention, the lockingmember is made to move in contact with the front cover as the frontcover is rotated between its closed position and opened position, and,even when the front cover is fully opened, the locking member can berestrained from moving unreasonably due to engagement with the frontcover.

Further, since the engaging area between the locking member and thefront cover is increased as compared with the turning force of the frontcover even when the cover is closed, the front cover can be lockedreliably and firmly. The locking and unlocking operations can beperformed extremely smoothly and reliably throughout the whole.

In the tape cassette of the invention, as shown in FIG. 28, each plugconsists of a crown portion 28a having a tool insertion groove 28bformed therein, a cylinder portion and a protrusion 28d projectinghorizontally from the lower end of the cylinder portion, and acompression coiled spring 40 is fitted on that plug between the crownportion 28a and the lower end protrusion 28d. The plug is formed in thecylinder portion thereof with a concave portion 28g so as to improve theinsertability thereof into the coiled spring. The plug is made of asynthetic resin or the like by means of monoblock molding.

On the other hand, through holes 20a (20b) (20 of FIG. 27A) and 21a(21b) (21 of FIG. 27A) into which the plug 28 is to be inserted arejoined by fastening together with screw or the like cylinder portions18a (18b) and 19a (19b) formed by monoblock molding in upper and lowerhalves 1 and 2 made of a synthetic resin or the like. The cylinderportion 18a (18b) of the upper half 1 is formed inside thereof with thecylindrical through hole 20a (20b), a groove 26a (26b) extending fromthe through hole vertically downwards, a stepped portion 31a (31b)serving to restrict the lower end position of the compression coiledspring 40, a slit-like positioning portion 24a (24b) for the plug lowerend protrusion 28d located in a different position from the verticalgroove 26 in terms of both angular and vertical positions, and anotherslit-like positioning portion 25a (25b) the angular and verticalpositions of which differ from those of the slit-like positioningportion 24a (24b), a triangular crest portion 27 (27a, 27b of FIG. 28)being formed additionally between the slit-like positioning portions 24and 25. While the cylinder portion 19a (19b) of the lower half 2 isformed inside thereof with a cassette casing positioning and sensorinsertion hole 21a (21b) and a sphere 23a (23b) in which the plug lowerend protrusion 28d can be moved freely up and down and rotated about itsaxis. In case that the cylinder portions 18 and 19 of the upper andlower halves 1 and 2 are to be joined together to form a through hole 22(22a, 22b of FIG. 28), surfaces 34 and 36 (34a, 36a, 34b, 36b of FIG.28) formed in the upper half for serving to restrict the rotation of theplug lower end protrusion 28d are aligned with surfaces 35 and 37 (35a,37a, 35b, 37b of FIG. 28) formed in the lower half 2 for serving torestrict the same. Further, as shown in FIG. 33, a substantiallysemicircular rib 33a (33b) and a plug rotation restricting surface 40a(40b) are formed integrally with an end surface 29 (29a, 29b of FIG. 28)of the cylinder portion 18 of the upper half 1 so as to extendvertically, and a concave portion 38a (38b) in which the above-describedvertical rib is to be fitted is formed in an end surface 30a (30b) ofthe cylinder portion 19 of the lower half 2.

According to the plug 28 and the through hole 22 constructed asdescribed above, as shown in FIGS. 29A, 29B, 30A and 30B, the lowerhorizontal protrusion 28d of the plug can be engaged with and insertedinto the through hole 20 and the vertical groove 26a (26b) of the upperhalf 1 against the compression coiled spring 40. As the plug 28 isinserted vertically downwards by means of a screw-driver 42 the tip endof which is brought into engagement with the tool insertion groove 28bof the crown portion 28a, the lower end of the spring is restricted by ahorizontal stepped portion 31. As the plug 28 is further displaceddownwards in the direction of Z, the plug crown portion 28a isrestricted by a horizontal stepped portion 39 with the horizontalprotrusion 28d at the lower end of the plug being displaced below theend surface 29 of the cylinder portion 18. In this case, by rotating inthe direction R through 90°, for example, as shown in FIGS. 30A and 30B,the plug lower end portrusion 28d is brought into engagement with theslit formed in the upper half 1 and displaced elastically up to thepositioning portion 25 due to the spring force. In this state, as theupper and lower halves 1 and 2 are fastened together with screws or thelike, the cylinder portions 18 and 19 are coupled (joined) together sothat the vertical insertion groove 26 for the plug lower end protrusion28d in the upper half 1 is covered with an upper end surface 30 of thecylinder portion 19 so as to prevent the plug 28 (28d) from coming offfrom the cassette casing 6.

In consequence, the plug 28 can be inserted and fitted into the throughhole 20 (22) very easily and reliably so as to be located at the upperposition thereof in the cassette casing.

Next, as shown in FIG. 32, as the screw-driver is inserted in the toolinsertion groove 28b at the top end of the plug so as to displace theplug lower end protrusion 28d down to a lower end restricting position32 (32a, 32b of FIG. 28) in the direction of Z against the spring forceand rotate in the direction of the arrow R through about 90°, the plugis positioned at the lower position 24. If it is tried to further rotatein this state, the rotation restricting surfaces 34, 35 and 52contribute to the prevention of excessive rotation.

When it is intended to change the plug 28 in the through hole 22, 23from the lower position 24 to the upper position 25, the plug 28 isdisplaced down to the lower plug position restricting surface 32 androtated counterclockwise through 90° while going over the triangularcrest rib 27 on the way and, thereafter, displaced upwards due to theelastic biasing force of the spring 40.

In this way, by changing selectively between the through holes 22 and 23as shown in FIGS. 31A, 31B, 27A and 27B, it is possible to change thedistance from the lower surface of the casstte casing to the plug lowerend 28e by extremely easy and exact operations such as to pressvertically, rotate in one direction, restrict the position and the like.

Further, as shown in FIGS. 33A and 33B, the upper and lower cylinderportions 18 and 19 are formed with the vertical circular rib 33 and theconcave portion 38 which is to be fitted on the vertical rib 33,respectively. By fastening together these cylinder portions 18 and 19with screws or the like, it is possible to prevent unexpected lateraldisplacement and deformation shown in FIG. 18, thereby preventing theserious defect such as disengagement of the plug or the like.

Next, the through hole formed at the center of the rear part of thecassette casing 6 and the plug to be inserted therein are the quite sameexcept the lengths of the cylinder portions 18 and 19 formed integrallywith the upper and lower halves 1 and 2 and the length of the plug 28,and therefore, explanation thereof will be omitted.

The present invention has been described above in conjunction with anembodiment, and however, the invention is not limited to this embodimentbut can be modified variously and effectively based on the technicalidea of this invention.

For example, in the present embodiment, the vertical semicircular rib 33is formed on the cylinder portion end surface 29 and the rib fittingconcave portion 38 is formed in the other cylinder portion surface 30with which the surface 29 is brought into engagement, and however, thesemicircular shape is not limitative. Further, the plug positioningportion is not limited in number to two as shown in the embodiment butcan be modified variously in number and configuration.

Incidentally, the present invention is applicable not only to the tapecassette for use in the video tape recorder but also to tape cassettesfor use in various recording/reproducing apparatus which record andreproduce various information by means of various recording andreproducing methods.

As described above, according to the present invention, the plug can beinserted into the through hole very easily and exactly and, at the sametime, since the through hole, the plug receiving portion and the plugcan be all formed by metal molds of simple structure, the cost can bereduced remarkably. In addition, even in case of positioning the plug inthe plural points, the changing operation can be performed easily andexactly. Further, since the cylinder portions can be coupled firmly witheach other, it is possible to prevent the fatal defects that the plug iscaused to rotate unexpectedly in the plural upper and lower positionsand that the plug is disengaged from the cassette casing, thereby makingit possible to position the plug at the plural stepped portions withoutfail. This makes it possible to transmit the information adequately fromthe cassette to the VTR or the like via sensor pin 41.

A third embodiment will be described with reference to the drawings.

The cylinder portion 18a (18b) of the upper half 1 is formed insidethereof with the cylindrical through hole 20a (20b), the groove 26a(26b) extending from the through hole vertically downwards, the steppedportion 31a (31b) serving to restrict the lower end position of thecompression coiled spring 40, another stepped portion 39a (39b), theslit-like positioning portion 25a (25b) for the plug lower endprotrusion 28d located in a different position from the vertical groove26 in terms of both angular and vertical positions, and anotherslit-like positioning portion 24a (24b) the angular and verticalpositions of which are differed from those of the positioning portion 25(a & b), the triangular crest projection 27 being formed additionallybetween the slit-like positioning portions 24 and 25.

FIGS. 34A to 34C show several embodiments of the plug in which the uppersurface portion of the horizontal protrusion 28d formed at the lower endof the plug so as to be opposed to the vertically downward crest-likeprojection 27 of the upper half 1, is formed in the substantiallytriangle pole. The projecting portion is formed integrally by taperedsurfaces 28h which are pushed up toward the center as shown in FIG. 34A,raised gradually to the right as shown in FIG. 34B or lowered graduallyto the right as shown in FIG. 34C while being formed with a round tipend 28i on the upper extension of the tapered surfaces, and the coiledspring 40 is fitted on the cylinder portion between the crown portion28a and the lower end protrusion 28d. These embodiments are alternativesto that of FIG. 28, with top surface 28c and side surface 28f.

FIGS. 35A and 35B are developments showing a part of the upper surfaceof the plug lower end protrusion 28d consisting of the tapered surfaces28h pushed up toward the center as shown in FIG. 35A and of the roundtip end 28i formed at the center, a part of the vertically downwardcrest-like projection 27 of the upper half 1, the movable space definedby the upper and lower halves 1 and 2, and part of the upper positioning(restricting) portion 25 (a & b) and lower positioning (restricting)portion 24 (a & b).

Incidentally, FIG. 35A shows the state of engagement between thecylinder portion 18 of the upper half 1 and the cylinder portion 19 ofthe lower half 2 in which the vertical circular rib 33 formed integrallywith the end surface 29 of the cylinder portion 18 is fitted in theconcave portion 38 formed in the upper end surface portion 30 of thecylinder portion 19, and FIG. 35B shows the state of engagement betweenthem in which the vertical rib 33 and the concave portion 38 aredispensed with.

In FIGS. 35A and 35B, the upper tapered surface 28h of the plug lowerend portrusion 28d makes an inclination θ with the horizontal while thevertically downward crest-like projection 27 of the upper half 1 makesan inclination γ with the horizontal, and the plug and the upper andlower halves are so formed as to satisfy the relation γ>θ or γ<θ. FIGS.35A and 35B show the state in the course of changing the plug lower endprotrusion 28d to the upper or lower position. As the tip end of thescrew-driver 42 or the like is brought into engagement with the groovedportion 28b formed in the crown portion 28a so as to move vertically androtate clockwise (or counterclockwise) through about 90° about the axis,even if the rotation is stopped unexpectedly during the rotation at anangle of 45° or so, for example, when the upper tapered surfaces 28h andthe round tip end 28i of the plug lower end protrusion 28d are to bebrought into engagement with the downward triangular rib 27 formed inthe half receiving portion, they are caused to slip in point or linecontact with each other because they each have limited horizontalportions, with the result in that the plug lower and protrusion 28d canbe received by force in either of the upper position 25 (a & b) and thelower position 24 (a & b). In consequence, the plug 28 is allowed toexist only at the height of the fixed position.

In FIGS. 35A and 35B, the upper tapered surfaces 28h of the lower endprotrusion and the tapered surfaces of the downward triangular rib 27 ofthe half are illustrated as being flat surfaces, and however, this isnot limitative but may be replaced by curved surfaces. It is preferredthat the radius of curvature of the round tip end 28i is made smallerfrom the viewpoint of the contact sliding ability.

Next, FIGS. 36A, 36B and 37A, 37B show different embodiments,respectively. The upper surface 28h of the plug lower end protrusionmakes an inclination θ with the horizontal and the round tip end 28i isformed on the upper extension of the tapered surface, and the plug andthe upper and lower halves are so formed as to satisfy the relation γ>θor γ<θ like the embodiment shown in FIGS. 35A and 35B. Even if thetapered surface is formed to be lowered gradually to the right as shownin FIGS. 36A and 36B or to be raised gradually to the right as shown inFIGS. 37A and 37B, the quite same effects can be obtained, with theresult that the plug lower end portrusion can be received by force inthe upper position 25 or the lower position 24 like the embodiment shownin FIGS. 35A and 35B.

In addition, the plug positioning portion is not limited in number totwo as shown in the embodiments but can be modified variously in numberand configuration.

Furthermore, a fourth embodiment of the present invention will bedescribed with reference to the drawings.

Referring to FIG. 38, the cassette main body 6 consists of the upperhalf 1 and the lower half 2, and the upper and lower halves 1 and 2 arecoupled with each other from above and below so as to form a unitedcasing.

A pair of reels 3 and 4 on which the magnetic tape 5 is wound areencased in the cassette, and the reel 3 (4) and a reel flange 43 arewelded to each other to become a single body. A clear window 44 throughwhich the amount of the remaining tape is to be confirmed is welded tothe upper half 1. A leaf spring 46 is attached to the upper half 1 so asto press the reel 3 (4) and the reel flange 43 toward the lower half 2.Further, the magnetic tape 5 stretched in the opening portion of thecassette is protected by the front cover 7.

As shown in FIG. 39, inside the upper half, ribs 45a and 45b arearranged on the inner surface of the upper half 1 and on the innersurface of the clear window 44, respectively, centering around thecenter of each reel. The ribs 45a and 45b are formed on the samecircumference with a diameter equal to that of the reel hub while beingmade equal to each other in height. Further, ribs 49 formed on the innersurface of the upper half 1 are arranged on a circumference with adiameter a little smaller inwardly than that of the reel flange whilebeing made lower than the ribs 45a and 45b in height. Tip ends of theribs 45a, 45b and 49 are each rounded variously lest they should bedamaged in case of contact.

Operation of the tape casette having the above construction will bedescribed below.

As the tape cassette 6 is loaded in the video tape recorder, the reel 3(4) and the reel flange 43 are lifted by a fixed amount with respect tothe upper half 2 and held in that state. In this case, a gap is to bemaintained between the ribs 45a, 45b and 49 and the reel flange 43.

However, when the tape cassette 6 is not loaded in the video taperecorder, the reel 3 (4) and the reel flange 43 are allowed to movebetween the lower half 2 and the ribs 45a and 45b formed on the innersurface of the upper half 1.

When this is the case, if the reel 3 (4) and the reel flange 43 move inparallel with the upper and lower halves 1 and 2, it is possible toregulate the movement by the ribs 45a and 45b. Further, even when theymove inclinedly, due to the difference in height between the ribs 45a,45b and the ribs 49, the movement of the reel 3 (4) and the reel flange43 can be first regulated by the ribs 45a, 45b and then the inclinationthereof can be regulated by the ribs 49, with the result that the reel 3(4) and the reel flange 43 can be prevented from coming in contact withthe magnetic tape.

As described above, according to this embodiment, since the ribs areformed on the inner surfaces of the upper half and the clear window atpositions located on the circumference with the diameter equal to thatof the reel hub and the circumference with the diameter equivalent tothe outside diameter of the reel flange, it is possible to prevent thetape from being damaged due to contact with the reel or the reel flange.

It is noted that although the ribs 45a, 45b and 49 are divided in thisembodiment, they may be formed continuously.

As has been described above, according to the present invention, byarranging on the inner surfaces of the upper half in which the reels areincorporated and of the clear window the ribs at positions located onthe circumference with the diameter equal to that of the reel hub andthe circumference with the diameter equivalent to the outside diameterof the reel flange, it is possible to realize an excellent tape cassettein which the tape can be prevented from being damaged due to contactwith the reel and the reel flange attributable to the deformation of thereel flange.

What is claimed is:
 1. A tape cassette having a cassette casingcomprising: upper and lower halves; a pair of upper and lower plugreceiving portions formed respectively in said upper and lower halves,said pair of upper and lower plug receiving portions being coupledtogether to form a through hole in said cassette casing; a plug insertedinto said through hole so as to be vertically movable and rotatableabout a vertical axis of said plug, said plug having an upper endprovided with a tool insertion groove, a lower end provided with ahorizontally projecting protrusion, and a spring fitted on said plug forurging said plug upwards; and a plurality of positioning portions withwhich said protrusion of said plug is brought into engagement so as tobe positioned while being restricted from rotating temporarily, saidplurality of positioning portions being provided in said through hole atpoints separated vertically and angularly about said vertical axis, sothat by bringing a tool into engagement with said tool insertion grooveformed in the upper end of the plug so as to make the plug movevertically and rotate about the vertical axis against a bias provided bysaid spring, said protrusion is selectively brought into engagement withone of said plurality of positioning portions, thereby to change avertical position of said plug,wherein the upper plug receiving portionincludes a vertical groove so that, when said plug is to be set, saidprotrusion of the plug is allowed to move vertically along said verticalgroove while being engaged with said vertical groove, said positioningportions are located at plural points having angular and verticalpositions which differ from an angular position and a vertical positionof said groove, at least one of said upper and lower plug receivingportions comprises means for closing said vertical groove with respectto said plurality of positioning portions when said upper and lowerhalves are fastened together to allow said plug to be positioned bybeing rotated and moved vertically only between said plural positioningportions, said protrusion of the plug is pressed and rotated so that theplug is fitted in one of said positioning portions while beingrestricted from rotating and, at the same time, fixed temporarily insaid upper half against the bias of said spring, and said upper andlower halves are fastened together to close said vertical groove by saidmeans for closing, so that said plug can be positioned by being rotatedand moved vertically only between said plural positioning portions,thereby preventing said plug from being disengaged from said cassettecasing.
 2. A tape cassette according to claim 1, wherein saidpositioning portions are formed by concave portions and a vertical ribwhich are formed in said upper plug receiving portion and a concaveportion which is formed in the lower plug receiving portion so as to befitted on said vertical rib, thereby providing positions at which saidplug is positioned vertically and fixed while being restricted fromrotating.
 3. A tape cassette according to claim 1, wherein said verticalgroove does not extend into said lower plug receiving portion.
 4. A tapecassette having a cassette casing comprising: upper and lower halves; apair of upper and lower plug receiving portions formed in said upper andlower halves, said pair of upper and lower plug receiving portions beingcoupled together to form a through hole in said cassette casing; a pluginserted into said through hole so as to be vertically movable androtatable about a vertical axis of said plug, said plug having an upperend provided with a tool insertion groove, a lower end provided with ahorizontally projecting protrusion, and a spring fitted on said plug forurging said plug upwards; and a plurality of positioning portions withwhich said protrusion of said plug is brought into engagement so as tobe positioned while being restricted from rotating temporarily, saidplurality of positioning portions being provided in said through hole atpoints separated vertically and angularly about said vertical axis, sothat by bringing a tool into engagement with said tool insertion grooveformed in the upper end of the plug so as to make the plug movevertically and rotate about the vertical axis against a bias provided bysaid spring, said protrusion is selectively brought into engagement withone of said plurality of positioning portions, thereby to change avertical position of said plug,wherein the upper plug receiving portionincludes a vertical groove so that said protrusion of the plug isallowed to move vertically along said vertical groove while beingengaged with said vertical groove when said plug is to be set, saidpositioning portions are located at plural points having angular andvertical positions which differ from an angular position and a verticalposition of said groove, said upper plug receiving portion includes acrest-like projection pointing vertically downwards and located at anintermediate point between two of said positioning portions, and theprotrusion of said plug is formed substantially in a shape of a trianglepole having an apex defined by a ridge extending radially outward withrespect to said vertical axis of said plug, said apex pointingvertically upwards to cooperate with said crest-like projection to guidesaid protrusion into one of said positioning portions.
 5. A tapecassette according to claim 4, wherein said protrusion has a horizontaldimension which is monotonically decreased in an upward directionparallel to said vertical axis.
 6. A tape cassette according to claim 5,wherein said horizontal dimension of said protrusion is measured in acircumferential direction normal to said vertical axis.
 7. A tapecassette according to claim 4; wherein said protrusion has a verticaldimension which is monotonically increased or decreased in acircumferential direction normal to said vertical axis.
 8. A tapecassette according to claim 4, wherein said horizontal protrusion ofsaid plug has a vertical dimension which is increased or decreased in acircumferential direction normal to said vertical axis, and aninclination Θ made by an upper surface of the protrusion with saidcircumferential direction and an inclination γ made by a surface of saidcrest-like projection with the horizontal are so set as to satisfy therelation γ>θ or γ<θ.
 9. A tape cassette according to claim 4, whereineach of said plurality of positioning portions comprises a verticallyextending straight groove.
 10. A tape cassette according to claim 4,wherein said protrusion of said plug has an upper surface inclined withrespect to said vertical axis, said upper surface of said protrusioncooperating with said crest-like projection to guide said protrusioninto said one of said positioning portions.